Have you tried to turn off WiFi Assist in Cellular setting? Airplane mode with WiFi? Network reset? Are you using public WiFi? If you attempted to download the update, go to iPhone Storage and delete the partial update and start fresh to trigger it again in Software Update.
No luck....
Still nothing wants to download. Streaming songs over the cloud works fine...everything else perfectly fine. But trying to update, download a song, or download an app? Nope lol acts like I have no service.